Lecture 19

Question 1

1. What are some examples of Gram-positive Bacteria?
2. What Phylum is Streptomyces in?
3. Where are Streptomyces found?
4. What are their features?
5. How many species of Streptomyces are there?
6. What is their life style?
7. What do they produce, or degrade?

Answer 1

1. Actinobacteria, Tenericutes, and Firmicutes.
2. Actinobacteria
3. Found is soil, degradation of complext materials (lignin, chitin).
4. Large group of filamentous, gram-positive Bacteria that form spores at the end of aerial filaments.
5. Over 500 species of Streptomyces (example: Streptomyces coelicolor).
6. Strict aerobes, use a wide variety of carbon sources, such as sugars, alcohols, organic acids, amino acids, and some aromatic compounds.
7. Produce extracellular hydrolytic enzymes degrade polysaccharides (starch, cellulose, and hemicellulose), proteins, and fats.

Question 2

1. What kind of antibiotics do Streptomyces produce?
2. How many Streptomyces antibiotics have found practical applications?
3. Why do they produce antibiotics?
4. What are their possible functions?

Answer 2

1. Streptomyces produce many clinically useful antibiotics, such as tetracycline and neomycin.
2. More than 60 Streptomyces antibiotics have practical applications (medical, agriculture, and industry).
3. Antibiotic production might be linked to sporulation (which is triggered by nutrient depletion).
4. To inhibit the growth of other organisms competing with Streptomyces cells for limiting nutrients during this critical transition to forming spores (survival structures).

Question 3

1. Where are Clostridium found? What do they form?
2. What are the life styles of Clostridium? What do they lack?
3. What is their mode of metabolism?

Answer 3

1. Found in soils; they are spore-formers (heat resistant).
2. Clostridium are obligately anaerobic. They lack cytochromes and an electron transport system for ATP synthesis.
3. Only use fermentative mode of metabolism (i.e., ATP via SLP).

Question 4

1. So, what Clostridia ferment?

Answer 4

1. One group ferments sugars: produce as major end product butyric acid. Some of these Clostridia also produce acetone and butanol. Some also fix nitrogen - example, Clostridium pasteurianum.
2. Another group ferments cellulose: major organisms decomposing cellulose anaerobically in soil.
3. Another group ferments amino acids: products of amino acid fermentation by Clostridia smell really badly, the odor from the putrefaction of animal carcasses is a result mainly of clostridial fermentation. Odorferous compounds produced: butyric acid, isobutyric acid, isovaleric acid, caproic acid, hydrogen sulfides, methylmercaptan, cadaverine, putrescine, and ammonia.

Question 5

1. What diseases can be caused by Clostridia?
2. How do they become pathogenic?

Answer 5

1. botulism: caused by Clostridium botulinum, tetanus: caused by Clostridium tetani, gas gangrene (and food poisoning): caused by Clostridium perfringens.
2. Traumatic tissue invasion by vegetative cells and spores leads to tissue destruction - proteolysis, collagen digestion, and toxin production.
   
   1. Fermentation of amino acids: H₂ and CO₂ (gases)

Question 6

1. What kind of bacteria are Lactobacilliales?
2. What do they lack?
3. What is their life style?
4. What are they limited to?
5. What are the two subgroups?

Answer 6

1. Lactic acid bacteria: produce lactic acid as a major or sole fermentation product.
2. Lack cytochromes: cannot carry out electron transport phosphorylation, obtain energy only by SLP.
3. All are anaerobes but most lactic acid bacteria are not sensitive to oxygen and can grow in its presence or absence, they are aerotolerant anaerobes.
4. Typically have only limited to biosynthetic ability and therefore have complex nutritional requirements, including needs for amino acids, vitamins, purines, and pyrimidines. Most obtain sugars and are found in habitats where sugars are present.
5. Homofermentative: produces a single fermentation product, lactic acid (ex. Streptococcus)
   
   1. Heterogermentative: produces lactic acid, ethanol and carbon dioxide (ex. Leuonostoc)

Question 7

1. What species of Streptococcus are pathogenic to humans and animals?
2. What other important roles do they play?

Answer 7

1. Streptococcus pyogenes: strep throat, Enterococcus faecalis: fecal streptococci, UTI.
   
   1. Streptococcus mutans: major role in dental caries.
2. Others play important roles in the production of fermented foods. Lactobacillus delbrueckii: yogurt

Question 8

1. What are Staphylococcus to humans and other animals?
2. What are the two major species that are recognized in humans?

Answer 8

1. Common commensals and parasites of humans and other animals, one can cause serious infections.
2. Major Species:
   
   1. Staphylococcus epidermidis: a nonpigmented, nonpathogenic organism usually found on the skin or mucous membrane.
   2. Staphylococcus aurens: a yellow pigmented species, normal resident of nose and throat; can cause disease when general health and immune system of host are weakened; produces an enterotoxin; common problem in poorly refrigerated foods, acute food poisoning; also commonly associated with pathological conditions, including boils, pimples, and pneumonia.

Question 9

1. What are the five major morphological types?
2. What kind of Bacteria are Cyanobacteria?
3. What are they responsible for? Hint: Has to do with the Earth!
4. How is oxygenic photosynthesis achieved?
5. What other organisms carry out this process?
6. What other modes of metabolism can cyanobacteria use?
7. What other mode of metabolism do some cyanobacteria use?

Answer 9

1. Unicellular, colonial, filamentous, filamentous heterocystous, and filamentous branching.
2. Cyanobacteria are oxygenic phototrophic Bacteria
3. Responsible for the conversion of Earth’s atmosphere from anoxic to oxic.
4. Achieved by the splitting of water, forms oxygen.
5. Also carried out by eukaryotic phototrophs (plants, algae); two photosystems, I and II.
   
   1. Not “blue-green algae”; these are Bacteria that have chl a (plant type chlorophyll); blue-green color comes from chlorophyll (green) and accessory pigments (phycobilins, blue).
6. Most are photolithautotrophs (do not use organic compounds). Energy obtained from sunlight, carbon from fixation of CO₂, electrons from reduced inorganic compounds e.g., H₂O, H₂S.
7. Some can carry out anoxygenic photosynthesis, using sulfide or sulfur as the electron donor; cyanobacteria are thought to have evolved from anoxygenic photosynthetic bacteria.

Question 10

1. What habitats are cyanobacteria found in?
2. How are cyanobacteria ecologically important?
3. How much of the oceans primary production do cyanobacteria account for?
4. What do aquatic types form?
5. What is another fixation some cyanobacteria can achieve?

Answer 10

1. Found in many kinds of terrestrial habitats, including deserts (endoliths in the antarctic dry valleys and cold deserts), tropical rain forest, mangrove swamps. Also found in many kinds of aquatic habitats, including freshwater streams and lakes.
2. Important contributors to CO₂ fixation. Synthesis of new organic material from CO₂ = primary production.
3. Cyanobacteria account for about 50% of the oceans primary production.
4. Form gas vesicles - regulate cell buoyancy so that cells can remain in a position in the water column where light intensity is optimal for photosynthesis by that type of cyanobacterium.
5. Many cyanobacteria are nitrogen fixers (reduction of N₂ to NH₃) - present especially in habitats that lack NH₃ and free amino acids make important contribution to nitrogen budgets of many habitats.

Question 11

1. What do some filamentous cyanobacteria form?
2. What is the significance of these structures?
3. What are these structures surrounded by?

Answer 11

1. Form heterocysts
2. Physiologically, biochemically, and structurally distinct from vegetative cells. Genes for nitrogen fixation are expressed in heterocysts but not in vegetative cells. They supply nitrogen to vegetative cells and receieve carbon and energy for nitrogen fixation from vegetative cells. Heterocysts do not make photosystem II (the oxygen is releasing photosystem).
3. Heterocysts are surrounded by a thickened cell wall containing large amounts of glycolipid, which serves to block the diffusion of O₂ into the cell. Nitrogenase is destroyed by oxygen; the heterocysts maintains an anoxic environment division of labor; nitrogen fixation (oxygen sensitivity), and oxygen generating photosynthesis (fixation of carbon).

Question 12

1. What groups of bacteria are considered Chlamydiae?
2. What are the features of Chlamydiae Bacteria?
3. What are some Chlamydial diseases?

Answer 12

1. Chlamydophila, Chlamydia, and Parachlamydia.
2. Small, obligate intracellular parasites of Eukarya cause a variety of diseases in animals, including in humans. Very small genomes: 0.5 to 1 Mb deficient in many metabolic functions dependent on host cell for nutrients.
3. Diseases:
   
   1. Chlamydia trachomatis: genitourinary tract, infections currently one of the leading sexually transmitted diseases.
   2. • Trachoma; scarring of the cornea, major cause of blindness in human.
   3. Chlamydia psittaci: pisttacosis; pneumonia, primarily in birds sometimes transferred to humans.
   4. Chlamydophila pneumoniae: Lung infections.

Question 13

Life cycle (infection cycle) of Chlamydia

1. What are the two cellular forms (body) of Chlamydia?
2. What is the elementary body?
3. What is the reticulate body?

Answer 13

1. Elementary & Reticulate bodies.
2. Small, dense cells. Relatively resistant to drying, non-multiplying cells specialized for infectious transmission. Serves as the means of dispersal. Chlamydia, primarily airborne invaders of the respiratory system.
3. Larger, less dense cells. Noninfectious vegetative cells function only to multiply (binary fission) inside host cells to form a large inoculum for transmission. After a number of divisions, these vegetative cells are converted into elementary bodies. The elementary bodies are released when the host cell disintegrates; they then can infect other host cells.